Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $13.61   5.859%   $14.4074   $14.41   $14.40   $14.40  
  Purchase #2 $237.70   10.208%   $261.9644   $261.96   $261.95   $262.00  
  Purchase #3 $92.82   3.520%   $96.0873   $96.09   $96.10   $96.10  
  Purchase #4 $63.45   11.612%   $70.8178   $70.82   $70.80   $70.80  
  Purchase #5 $45.85   13.204%   $51.904   $51.90   $51.90   $51.90  
  Purchase #6 $168.35   8.241%   $182.2237   $182.22   $182.20   $182.20  
  Purchase #7 $67.78   11.769%   $75.757   $75.76   $75.75   $75.80  
  7 purchase totals = $689.56       $753.1616   $753.16   $753.10   $753.20